Democracy and Class Struggle appreciates this Philosophical work of Mao Zedong as a summation of the New Philosophy that emerged in class struggle in the Soviet Union and China in the 1930's.
The extent of the influence on Mao of the New Soviet Philosophy has been the subject of debate and I find myself in agreement with Nick Knight on this issue in link below.
Democracy and Class Struggle upholds the Marxist Leninist roots in Maoism and we do not reject it like the Avakians and other revisionists
We will address this question in more detail as we approach 2017 when we will celebrate the intellectual advances of the Soviet Union but also visit their historically imposed limitations.
For those that want to study the advance in Marxist Philosophy in Soviet Union in the 1930's this textbook edited by Comrade Shirokov published in 1941 is a good summary.
Also here is a sampler from Nick Knights work on Marxist Philosophy in China: From Qu Qiubai to Mao Zedong, 1923–1945